The present invention relates to a method of operating a carding arrangement which has a drum with a drum fitting and a plurality of card flats. Each card flat is provided with a card flat fitting, wherein the card flat can move relative to the drum along a predetermined path while maintaining a predetermined distance between the drum fitting and the card flat fitting. A running surface of each card flat fitting is in contact along the predetermined path with a guide surface defining the predetermined path. The invention also relates to a card flat for carrying out the method.
Cards operating according to the aforedescribed method are used to orient individual fibers of a raw material, for example material used in the manufacture of yarn. The operation of such a card is as follows: The card includes basically a drum and a several card flats. The second drum is essentially shaped as a circular cylinder and includes a fitting arranged on its outer surface. The fitting of the card is formed of individual wire hooks inserted into a rubber fabric. Alternatively, fittings in the form of saw-tooth wires which helically surround the cylinder axis of the drum, can also be employed. During the operation of the card, the drum is rotated about its cylinder axis.
The card flats are secured to a continuous transport element, such as a transport belt or a transport chain. The transport element can be used to move the card flats relative to the drum along a predetermined path extending approximately parallel to the outer surface of the drum and to then return the card flats above the predetermined path. The transport direction of the card flats along the predetermined path opposes the rotation direction of the drum. The side of each card flat which faces the drum fitting along the predetermined path, has a card flat fitting. The card flat fittings of the card are formed as a wire fabric which is inserted into a rubber fabric.
To orient the individual fibers parallel to each other, raw material provided, for example, in the form of cotton flakes, is supplied to the drum by a taker-in or a supply drum. The taker-in includes a saw-tooth fitting made entirely of steel. The supplied material is captured by the drum fitting and entrained in the rotation direction of the second drum. The fibers entrained by the drum fitting are flattened by the card flats which move along the predetermined path in a direction opposing the rotation direction of the drum. This process produces on the drum fitting a fine pile of oriented fibers which can be removed from the drum with a stripper roller (not shown) for further processing.
For proper carding, the tips of the card flat fittings moving along a predetermined path in the opposite direction of the rotation direction of the drum have to maintain a predetermined distance of approximately 0.15 to 0.18 mm from the tips of the drum fittings. For this purpose, the individual card flats typically have card flat rods supporting the card flat fittings, with hardened guide pins fixedly secured in the card flat rods. The card flat running surfaces formed by the guide pins contact at least along the predetermined path a sliding guide which is typically made of plastic. Card flats of this type are disclosed, for example, in U.S. Pat. No. 5,473,795.
It has been observed that with cards operated in the manner, the carding effect deteriorates with increasing operating time. The drum fittings and the card flat fittings may also be damaged with increasing operating time. These defects are commonly eliminated by applying new fittings to the drum and the card flat, thereby eliminating the defects caused by wear of the fittings. However, it has been observed that even after applying new fittings to the drum and the card flats, the original carding efficiency obtained when the card was first put in service, could no longer be attained and that the fittings were again damaged after operating only for a short time.